1. Field of the invention
This invention relates to an apparatus for accumulating a filiform element travelling at two different speeds when entering and exiting the apparatus.
2. Description of the Prior Art
Preferably, the filiform element is an optical fiber which leaves a multifibering machine at a first speed and which enters a cabling machine at a second speed. In normal operation, the first and second speeds are equal.
However in pratice it often turns out that the two speeds, although slaved to each other, are sometimes not the same, which results in slowing down of travel in the multifibering machine or the cabling machine, or momentary stoppage of one the machines for repair, replacement of parts or the like. In any case, slowing or stoppage of one of the machines necessarily means that the other machine experiences the same.
To overcome this operational interdependence of the multifibering machine and the cabling machine, it proves necessary to place an optical fiber accumulation apparatus between the two machines in order to absorb the differences between the first and second speeds, without damaging the optical fiber. Thus if the multifibering machine upstream of the apparatus slows or stops, the quantity of optical fiber accumulated will diminish, and if the cabling machine downstream of the apparatus slows or stops, the quantity of optical fiber accumulated will increase. In practice, the ability of the apparatus to absorb differences and irregularities in the travel speeds will depend on the apparatus storage capacity and therefore essentially on its dimensions.
An accumulation apparatus having the above features is disclosed by German patent application No. 1,139,085. In this apparatus, the filiform element to be accumulated is an iron wire. The apparatus is inserted in a roll line. Upstream of the apparatus the wire passes through a vertical tube followed by an arm tilted in relation to the tube and attached to it, or a truncated funnel coaxial with the tube and connected to it. The tube and the arm or funnel are rotated above a tank in the form of a fixed cylindrical accumulation drum and are driven coaxially to it by a gear train coupled to a motor. The rotation of the arm or funnel thus allows the iron wire to be deposited in stacked circular coils on the bottom of the drum, the wire coils being kept concentric against the cylindrical internal wallside of the drum. The wire is drawn at a second low travel speed through a central orifice in the bottom of the drum.
However, such an apparatus is not usable to accumulate an optical fiber because of the fact that the optical fiber is extremely fine, with a diameter of a few tenths of a millimeter, and can not be concentrically stacked. In practice, the coils of optical fiber sag towards the middle of the coils, causing them to become entangled and thus creating a risk of embrittlement, or even breakage as the fiber is drawn out of the drum. In addition, as will be seen later on, certain special precautions need to be taken when accumulating an optical fiber, in particular with regard to the bend radius imposed on the fiber, which should never exceed a minimum radius below which the physical and mechanical properties to the optical fiber are impaired.